Trifluoroethylene (HFO-1123), which has a low global warming potential (GWP), is greatly expected in recent years as a new refrigerant which may replace difluoromethane (HFC-32) and 1,1,1,2,2-pentafluoroethane (HFC-125) which are greenhouse gases.
In this specification, abbreviated names (e.g. refrigerant numbers) of halogenated hydrocarbon compounds are described in brackets after the compound names. As the case requires, the abbreviated names are employed instead of the compound names.
Heretofore, a method for producing HFO-1123 from 1,1,1,2-tetrafluoroethane (HFC-134a) which is a relatively inexpensive material has been known. For example, Patent Document 1 discloses a method of subjecting HFC-134a to dehydrofluorination in a gaseous phase using a metal fluoride as a catalyst. Further, Patent Document 2 discloses a method of reacting HFC-134a with a metal hydroxide such as calcium hydroxide in a gaseous phase.
However, either of the methods disclosed in Patent Documents 1 and 2 has the following problems since HFC-134a in a gaseous phase is brought into contact with and reacted with a solid reactant forming a fixed bed.
(1) Since it is difficult to uniformly mix particles of the solid reactant with HFC-134a and bring them into contact with each other, the degree of conversion of the solid reactant is low. Further, since the reactivity in the reaction of forming HFO-1123 from HFC-134a is low, it is necessary to bring HFC-134a into contact with the solid reactant for a long period of time.(2) Since the heat removal efficiency is poor when a fixed bed is used, hot spots are likely to form. Accordingly, side reactions such as cleavage of a carbon-carbon bond of HFC-134a are likely to occur, and by-products such as low molecular weight hydrocarbon compounds such as methane, ethylene and propylene and polymer carbon (graphite) are likely to form.(3) Since the amount of by-products such as polymer carbon is large, the polymer carbon is attached to the surface of the solid reactant, whereby the degree of conversion of HFC-134a is remarkably lowered with time. Thus, stable production of HFO-1123 is difficult.